Toshiba e-STUDIO520 Service Manual page 251

(4) Developer unit
The developer unit of the e-STUDIO850 has a different structure (driving gear) from that of e-
STUDIO520/600/720 due to its copy speed. The developer unit of the e-STUDIO520/600/720
has a protrusion on its rear side to prevent a wrong installation.
• Developer material
The developer material consists of the carrier and toner. The carrier is a conductive ferrite
whose size is 30-100 µm. The toner consists of 5-20 µm size resin particles. The developer
material requires a periodic maintenance since it deteriorates in a long-term use and print
images may be influenced by this deterioration.
• Mixer
The carrier and toner generate a friction when the developer material is mixed. The carrier is
positively charged while the toner is negatively charged, and thus the toner is adhered on the
drum by static electricity caused by this charging.
• Paddle
The paddle supplies the developer material mixed by the mixer to the transport sleeve. Also
the paddle returns the developer material separated from the lower developer sleeve to the
mixer section.
• Transport sleeve / Developer sleeve (Magnetic roller)
These sleeves are aluminum rollers which include a magnet in each. This magnetic force
attracts the developer material to form a magnetic brush. This magnet is fixed, therefore only
the sleeves are rotated. By this rotation, the developer material is transported from the trans-
port sleeve to the developer sleeve, and the magnetic brush formed by the developer sleeve
sweeps over the drum surface, thus the development is performed.
• Doctor blade
The doctor blade controls the amount of the developer material transported from the transport
sleeve so that the magnetic brush of the developer material can contact with the drum surface
properly.
• Auto-toner sensor (S12)
The ratio of the carrier and toner (= toner density) in the developer material should constantly
be fixed at a certain level for a correct image printing. The auto-toner sensor (S12) detects the
inclusion ratio of the toner in the developer material with a magnetic bridge circuit. When the
toner becomes insufficient, the new toner supply motor (M6) and the hopper motor (M7) are
driven to supply the toner from the toner cartridge and the recycle toner hopper.
• Scattered toner recovery roller
This roller catches the toner scattered from the developer sleeve and puts the caught toner
into the developer unit, so that the scattered toner will not fall out of the developer unit.
(5) Developer unit drive section
The developer unit is driven by the developer unit motor (M10).
(6) Developer unit fan (M31) / Toner filter
The developer unit fan (M31) suctions the toner scattered out of the developer unit, and the suc-
tioned toner is then collected at the toner filter through the duct.
(7) Duct in fan (M30)
This fan cools down the developer unit.
March 2005 © TOSHIBA TEC e-STUDIO520/600/720/850 DEVELOPER UNIT
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